PROJECT SUMMARY/ABSTRACT Our recently completed Phase 1 animal studies demonstrated the ability of our novel second generation partial (p)MHC construct, DR?1-hMOG-35-55, to treat acute and chronic EAE with potency comparable to the parent RTL1000 molecule (pDR2-MOG-35-55) in matched DR2-Tg mice and in DR2 negative mismatched mice. Having met our Phase 1 milestones, our Phase II application will produce a fully humanized DR?1-hMOG-35-55 molecule and assemble preclinical data necessary to support a pre-IND meeting with FDA, at which critical input will be obtained in order to enable the filing of a Phase 1 safety and tolerability study in humans. These data will include characterization of the pharmacokinetics (PK), toxicokinetics (TK) and downstream effects of potential anti-drug antibody (ADA) production. Additionally, this study will assess as an in vivo biomarker the intrinsic activity of DR?1-hMOG-35-55 to inhibit peripheral blood mononuclear cell (PBMC) expression of CD74, the major cellular receptor for macrophage migration inhibitory factor (MIF) that has been implicated in MS disease progression both in the literature and in samples from MS subjects. Our proposed studies are patterned after the preclinical development plan that enabled RTL1000 human clinical trials and are designed to stage DR?1- hMOG-35-55 for cGMP manufacture and formal preclinical studies necessary for a Phase 1 clinical trial in human subjects. The clinical protocol to be supported by these preclinical studies will generally follow that used for RTL1000 (Double-Blind, Placebo-Controlled, Phase 1, Dose-Escalation Study of the Safety of a Single Dose of RTL1000 in Subjects with Relapsing Remitting or Secondary Progressive Multiple Sclerosis) which demonstrated that RTL1000 was safe and well tolerated at doses <60mg (1,000g/kg). Doses of DR?1-hMOG- 35-55 to be infused in the human Phase 1 trial will be guided by pre-IND discussions with FDA and will depend on the minimal effective dose (MED) as well as the maximum tolerated dose (MTD) to be determined for both sexes in this proposal. Data from our Phase 1 STTR has established that a higher dose of DR?1-hMOG-35-55 is required for inhibiting T cell activation in vitro and for treatment of chronic EAE in females vs. males, thus necessitating establishment of separate MEDs and overlapping efficacy curves to yield a common dose range. It is anticipated that these studies will facilitate filing of a successful IND for initiating therapeutic trials with DR?1- hMOG-35-55 in subjects with MS.